What is the first action taken during the cleanup step if the active player's hand exceeds their maximum hand size?

During the cleanup step, if the active player has more cards in their hand than the maximum hand size allows, the very first action that takes place is that the player discards enough cards to bring their hand size down to the maximum allowed. This is in accordance with the rules governing hand size, which dictate that a player cannot have more than seven cards in hand unless a specific card effect states otherwise.

It’s important to note that the cleanup step is part of the turn structure, following the combat and main phases. At this point, any effects that end at the end of turn have already resolved, and players have the opportunity to tidy up their hands. Consequently, any excess cards must be discarded in this step before moving forward with the next player's turn or through any further actions.

The other options relate to other aspects of the game but do not occur first in the cleanup step. For instance, shuffling graveyards into libraries or removing damage from permanents all happen at different times in the turn cycle but not as a direct consequence of exceeding maximum hand size.